Research On The Establishment Of Finite Element Model Of Multiphase Materials For L4/5 Intervertebral Disc Common Protrusion And Rotational Manipulation Loading

Objective:To determine the properties of lumbar L4/5 disc herniation,including colloid,fibrosis and ossification,by using CT gray value detection of lumbar disc herniation and pathological examination of protrusion tissue after nucleus pulposus extirpation.By uploading volunteer's non-postoperative CT data to finite element modeling software,build three multiphase material three-dimensional finite element models with complete functional segments in common areas of L4/5 disc herniation,i.e.layer ?,region 2,region B,and the differences of material properties of L4/5 disc herniation in the cases of colloid,fibrosis and ossification were analyzed.At the same time,the loading force under different working conditions of the fixed-point rotational reduction method in sitting position is simulated on three models,and the displacement and stress variation differences of intervertebral disc and lumbar facet joint process under different material properties lumbar model are analyzed,and which direction and strength is the safest when the loading force of the rotational reduction method in sitting position is studied.Methods:The lumbar CT three-dimensional reconstruction data of three lumbar intervertebral disc herniation volunteers were collected.The protruding objects were located in the common region I,layer 2,region B.After CT gray value detection and pathological detection of the protruding objects,the material properties of colloid,fibrosis and ossification were determined respectively.The non-operative lumbar CT three-dimensional reconstruction data were used to build models in medical image processing software,reverse engineering software and finite element analysis software.Three simple models of lumbar L4/5,layer 1,region 2,region B protruding vertebral bodies with complete functional segments were obtained,namely colloid,fibrosis and ossification models respectively,and theoretical verification was carried out.Based on the literature,three different angles of mechanical working conditions of the sitting rotation reduction method are loaded on each model,and the lower surface of L5 vertebral body is fixed in finite element analysis software to simulate the loading forces of lateral flexion 6°,rotation 2°,and forward flexion 6°,9°,and 12° respectively,and the stress analysis is carried out,and the stress situation of the facet joint contact surface of each model under three different working conditions of the sitting rotation method is observed.Results:(1)The material properties of disc herniation can be judged by CT gray value detection and pathology detection;(2)Three simple models of lumbar L4/5? layer 2 region B protruding vertebral body with complete functional segments of spinal column were established,namely colloid model,fibrosis model and ossification model.(3)Stress of zygapophysial joints: The stress concentration side of the small joint contact surface in each model is mainly located on the rotation side when the rotation reduction method is loaded.Conclusions:(1)When the root of L4 spinous process is used as the fulcrum of the push plate for rotational reduction,the stress of the articular process joint is mainly concentrated on the rotational side of three different lumbar models.(2)Three finite element models of colloid,Fibrosis,Osteogenesis model,the L4/5 segmental disc herniation can be established using finite element software.(3)Under the three mechanical loading conditions,all forces are concentrated on the posterior lateral side of lumbar disc herniation,and the surface stress and displacement of L4/5 disc have different degrees of changes.(4)When the rotation reduction manipulation acts on the anterior flexion movement of 9 degrees,the lumbar spine has the largest displacement and the smallest stress in the colloid model,which is beneficial to guide the clinical manipulation.When the rotation reduction manipulation acts on the anterior flexion movement of 12 degrees,the lumbar spine has the largest displacement and the smallest stress in the colloid model,which is beneficial to guide the clinical manipulation.(5)When the rotation reduction manipulation acts on the anterior flexion movement of the lumbar spine has the largest displacement and the smallest stress in the colloid model,which is beneficial to guide the clinical manipulation.